L2 IO Transfer

1
L2 I/O Transfer

• James T. Linnemann
• Michigan State University
• Trigger Meeting
• February 20, 1998

2
Current Status
MBus

VME
TCC
Wo r ker
Admin
VBD
MPM
MBT
SCL
Outputs to Global (preprocessors only)
L3


8 VME slots minimum

Dec Alpha (Unix)
JTL, MSU 12/18/97

3
L2 Global Inputs

• L2 Global Inputs via MBT card
• MBT propose Fiber 160 Mb/s
• Requires SLIC have one Fiber output
• Question is SCL Fanout Fiber or Copper
• Advantages
• Simpler to set up than copper (balancer,
  transformer
• Less fussy to make work
• separation of grounds (if move out of MCH)

4
L2 Input Fiber, continued

• Disadvantages of Fiber
• FIC needs fiber to serve MBT, copper for SLIC
• more expensive 60/channel or so
• including cable/fiber?
• Cost for both ends or one?
• beware of finger prints
• patch panel more complex/costly
• needed to re-cable if L2 in Fixed Counting House
  and MCH moves

5
Fiber Input Converter

• Inputs
• only g-link transfer from L1 CFT/PS
• assuming 8/10 or 16/20 encoding for integrity
• g-link
• Speed requirements of STT input
• recycle engineering of VRB inputs (STT needs raw
  data)
• Outputs (Cypress)
• 160 Fiber (MBT)
• 160 Copper (SLIC)

6
L1 CFT Outputs to FIC

• Begin and End Event as g-link Symbols
• not as values of data
• Not in Gray code
• Padded to 16 B
• 3B Crossing number (to match L1 accept)
• Header and Trailer consistent with L2G input
  specs
• PS data on fibers separate from CFT fibers
• Bytes produced so no swapping on FIC needed?

7
Byte (non-) swapping

• Sources responsibility NONE on MBT card
• Send bytes to Cypress in order such that when
  assembled in Alpha, they have specified order
  (B1, B2, B3, B4)
• Will provide final spec so multi-byte
  quantities (3B crossing number, 2B eta, etc) come
  out right in Alpha
• Do L1CFT 2B quantities have fields crossing Byte
  boundaries?

8
L2G Header/trailer

• 12B Header, 4B Trailer
• Tradeoff
• 4B Header word fixed vs.
• 4B Trailer one 4B Header word
• Opinions?

9
L2G Header, Trailer Matched

• H1 Length (1B), Format (2B), Object Length(1B)
• H2 Source(1B),Rotation(2B), Bunch(1B)
• H3 Status(1B),Version(1B),Switches(1B),Nobj(1B)
• Trailer H2

10
L2G Header, Fixed Word

• H1 Length (1B), Format (2B), Object Length(1B)
• H2 Nobj(1B),Rotation(2B), Bunch(1B)
• H3 Source(1B),Status(1B),Version(1B),Switches(1B)
  
• TrailerSource(1B),Rotation(2B), Bunch(1B)

11
FIC for raw data?

• More complex beast!
• Gray Code conversion required
• Need to generate/resynch crossing number
• bus to all channels
• Need to generate header/trailer
• need to pad to 16B?
• REQUEST g-link start/end symbols
• else recognition task needed to count events in
  buffers
• Considerable Escalation over L1 FIC
• Defer design until proven to be needed